In a solid polymer electrolyte fuel cell system, the proton-exchange membrane must be maintained in a saturated hydrous state by supplying water to the fuel cell, in order to ensure the proton conductivity electrolyte function. As one method for securing the water for hydration of the proton-exchange membrane, there is a method that provides a water-permeable humidifier that humidifies the gas supplied to the fuel cell by recovering the moisture in the discharge gas of the fuel cell.
The fuel cell disclosed by JP2001-256989A, which was published by the Japan Patent Office in 2001, comprises, in addition to a water-permeable humidifier, a water recovery device for recovering water in the fuel cell discharge gas, and auxiliary humidification means for humidifying the supply gas by means of the recovered water thus recovered by the water recovery device. The water recovery device is constituted by a vapor separation device and a recovered water storage tank, and the auxiliary humidification means are constituted by a check valve, a recovered water supply pump, auxiliary humidification piping, and an injector, and so forth. During startup of the fuel cell, the recovered water in the recovered water storage tank is transferred by means of a recovered water supply pump, injected in the form of a mist by the injector, and then supplied to the gas supply side of the fuel cell. The proton-exchange membrane can thus also be humidified during startup of the fuel cell.